The inadequacy of current carbon storage assessment methods for rewilding: A Knepp Estate case study
Data files
Nov 28, 2023 version files 86.64 KB
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above_vs_below_total_pt1_feb23.csv
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README.md
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total_opwall_adj_dbh_feb23.csv
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Abstract
- In the context of global climate change mitigation, carbon storage in woody vegetation plays a crucial role. Recognising the value of the i-Tree Eco model for carbon storage in urban and forestry settings, this study aimed to explore its applicability to rewilded landscapes. Using direct measurements from destructively sampled scrub from the Knepp Estate, our goal was to determine the model’s suitability to this landscape.
- Our findings reveal that these methods are not appropriate for multi-stemmed trees below browsing height, as we observed no significant relationship between stem basal diameter and height. The i-Tree tool's assumption of belowground biomass being 26% of aboveground biomass may not be applicable to herbivore-influenced landscapes. Additionally, we found that on average, scrub at Knepp had more biomass below the ground than above, with a root:shoot ratio of 1.07, which is more than 4 times the amount predicted by current models using the 0.26 estimate ratio.
- This study underscores the need for novel allometric approaches that consider species-specific biomass and the impact of external factors, such as herbivory, on carbon storage. Accurate carbon accounting in future rewilding projects is essential for their contribution to both biodiversity enhancement and climate change mitigation.
- While the i-Tree Eco model provides valuable insights for many ecosystems, our findings suggest that its applicability may be limited in scrubland ecosystems, especially in rewilded landscapes where natural processes create semi-stable scrub and open wood pastures. Nonetheless, with suitable adjustments or when complemented with other methods, the i-Tree Eco model could be a valuable tool for specific scrub or rewilding scenarios.
README: The Inadequacy of Current Carbon Storage Assessment Methods for Rewilding: A Knepp Estate Case Study
https://doi.org/10.5061/dryad.76hdr7t31
Brief Summary of Dataset Contents:
The dataset from the study conducted at Knepp Estate primarily involves direct measurements of scrubland vegetation, focusing on evaluating the i-Tree Eco model's applicability to rewilded landscapes. The study's findings revealed limitations of current methods in estimating carbon storage for multi-stemmed trees in herbivore-influenced landscapes, suggesting the need for novel allometric approaches. The data has been split into two datasets, here's a brief overview of each:
Data Set 1: Total_Opwall_Adj Dbh_Feb23
- Purpose: Utilises an allometric model by iTree Eco to assess tree biomass at the Knepp Wildland project.
- Data Collected: Includes species, scientific name, height (in meters), diameter at breast height (DBH) (in centimeters), number of stems, and presence of species-specific allometric equations.
- Columns:
- species: The common name of the tree or shrub.
- scientific name: The scientific nomenclature.
- height (m): The height of the tree/shrub.
- dbh (cm): Diameter at breast height.
- no_stems: Count of stems for each tree/shrub.
- present: Indicates if a species-specific allometric equation is available.
- proxy: Refers to the phylogenetic class used by iTree for biomass estimation.
Data analysis:
- Software: i-Tree Forecast Eco v6.0.22
- Description: Used for estimating potential carbon storage. It allows for adjustments in measurement techniques, such as measuring the diameter at ground level when standard diameter at breast height (DBH) cannot be taken.
- Statistical analysis:
- Tree Height and DBH Relationship Analysis: Using R studio version 2022.7.2.576 - Spearman’s Rank Correlation and Siegel nonparametric linear regression analysis were employed to evaluate the relationship between tree height and DBH. Trees were divided into two height categories: above and below 2.5 meters, corresponding to the browse line height.
Data Set 2: Above Vs Below_Total_Pt1_Feb23
- Purpose: To compare aboveground and belowground biomass weights for a sample of trees and evaluate the i-Tree model's root:shoot ratio assumption.
- Data Collected: Biomass weights (in grams) of 39 destructively sampled trees and shrubs, to compare the aboveground (AGB) and belowground biomass (BGB) to the predicted estimate of the i-Tree model.
- Columns:
- species: The common name of the tree or shrub.
- agb_weight (g): Aboveground biomass weight.
- Bgb_weight (g): Belowground biomass weight.
- I_tree bgb (g): The predicted belowground biomass using the i-Tree model, calculated as 0.26 times the aboveground biomass.
- root:shoot ratio: A comparison metric of belowground to aboveground biomass.
Destructive Sampling Methodology: The extraction of above- and belowground plant material.
Statistical analysis:
- Statistical Analysis Software: R Studio version 2022.7.2.576
- Graph Creation: ggplot2 package in R Studio
Analytical Techniques:
- Root:Shoot Ratio Evaluation: A one-sample t-test was used to compare the measured root:shoot ratio with the i-Tree Eco model's predicted ratio of 0.26. This was crucial for assessing the model's accuracy in predicting belowground biomass.
Sharing/Access Information:
- Links to Other Publicly Accessible Locations of the Data: Currently not provided in the document.
- Data Derived From Sources: The study references several external sources, including publications and databases like GlobAllomeTree and the i-Tree database, which informed the methodology and analysis.